1. Technical Field
The present invention relates to a liquid ejecting head, a liquid ejecting apparatus, and a piezoelectric element.
2. Related Art
Piezoelectric materials, which are charged by distorting their crystals or are distorted by being placed in an electric field, are widely used in sensors, and in actuators used in ink jet printers or the like. PZT (lead zirconate titanate, Pb(Zrx,Ti1−x)O3) is a typical piezoelectric material. Unfortunately, PZT contains lead (Pb). From the viewpoint of reducing the environmental load, a lot of research and development has been conducted for lead-free piezoelectric materials.
Researched and development has recently been conducted for lead-free piezoelectric thin films and thin-film piezoelectric elements using the lead-free piezoelectric thin films. The thin-film piezoelectric element can be manufactured, for example, by forming a piezoelectric thin film to a thickness of several micrometers or less on an electrode disposed on a substrate and forming an upper electrode on the piezoelectric thin film. This process is performed as finely as semiconductor processes, and accordingly can advantageously provide a structure including thin-film piezoelectric elements arranged at a higher density than a structure including piezoelectric elements using a bulk piezoelectric material. For example, BiFeO3—BaTiO3 materials disclosed in JPA-2009-252789 exhibit superior characteristics as a lead-free thin-film piezoelectric material.
For forming a piezoelectric thin film by a liquid phase method, such as spin coating, the piezoelectric thin film is formed by applying a precursor solution onto a first electrode, and crystallizing the coating of the precursor solution. Then, a second electrode is formed on the piezoelectric thin film to complete a piezoelectric element.
JP-A-2009-242229 proposes that a (Ba,Bi)(Ti,Fe,Mn)O3 lead-free piezoelectric film be formed by a gas-phase method, such as pulsed laser deposition (PLD).
When a piezoelectric element was formed using a BiFeO3—BaTiO3 piezoelectric material, however, the BiFeO3—BaTiO3 piezoelectric thin film was easier to crack than PZT thin films. It was thus found that BiFeO3—BaTiO3 piezoelectric materials are difficult to put to practical use. This disadvantage can arise not only in liquid ejecting heads, but also in piezoelectric actuators and sensors.